The Modification And Characterization Of Soluble Dietary Fiber From Tomato Peels

Tomato peel was rich in dietary fiber?DF?,but the content of soluble dietary fiber?SDF?was under 10%,which need to be increased to improve the taste and nutritional value of DF.Alkaline hydrogen peroxide?AHP?,hydrochloric acid-ethanol?HAE?and enzyme hydrolysis?EH?were designed as three different modification methods to recycle tomato peel for improving the extraction yield of SDF,named as A-SDF,H-SDF and E-SDF.The structural and functional properties of SDFs were studied to get the optimal modification method.By comparing the gelling performance of B-SDF with different ions(Fe²⁺?Ca²⁺and Mg²⁺)and the effect of pH,which provids theoretical basis and preliminary practical experience for the further development of DF.The main research contents are as follows:Firstly,the structural characteristics of A-SDF,H-SDF and E-SDF were compared.The molecular weight and negative potential of A-SDF decreased to 1.30×10⁵ Da and-39.5 mV.A-SDF,E-SDF and O-SDF were composed of seven monosaccharides,while H-SDF did not contain rhamnose.Modified SDF has increased the content of galacturonic acid.Infrared spectra images showed that the modified SDFs cause the hydrolysis of some functional group bonds in the SDF structure to decrease or disappear.The surface of modified SDFs were smoother than O-SDF.Then,the rheological properties of SDF from tomato peel before and after modification were studied.All SDFs showed shear thinning behavior,but the apparent viscosity of the modified SDF was decreased.In the presence of Ca²⁺,all SDFs formed colloids,and A-SDF and H-SDF showed good gelation properties.Next,the functional properties of O-SDF and modified SDFs were studied.Compared to O-SDF,modified SDF has increased the bile acid binding capacity and glucose absorption capacity in vitro,especially A-SDF and H-SDF.In general,compared to H-SDF and E-SDF,A-SDF had better rheological and functional properties.Finally,based on the optional modification conditions of AHP,the extraction rate of SDF from tomato peel increased from 7.9%to 27.5%,named as B-SDF.From the TEM images,B-SDF with porous structure and multi branches,while O-SDF had compact structure.Different concentrations of B-SDF and O-SDF solution all showed shear thinning behavior,but 4%?w/v?B-SDF solution had lower viscosity.The varied range of viscosity was decreased,indicating the dissolving capacity of B-SDF was improved.In addition,B-SDF could perform the best gelling property with Ca²⁺under pH 5,improving the water holding and bile acid binding ability.After that,we can explore the specific mechanism of the three modification methods and other physiological functions of modified B-SDF,and apply the gelling characteristic of B-SDF-Ca²⁺to food processing.